2014 Mountain Bike Gear

First Ride: SRAM's X01 Single-Ring Drivetrain

We test the impressive new group on a 5,000-foot descent in Whistler, British Columbia.

matt phillips

(Photo by To test the new group, we rallied down Whistler's Top of the World trail. (Adrian Marcoux))

Last year, SRAM invited cycling journalists to test out its then new XX1 11-speed drivetrain during Whistler’s Crankworx festival. Those attending boarded lifts, which whisked them to Whistler’s 7,494-foot-high summit, and then they tore down the mountain’s Top of the World Trail to test the new drivetrain.

This year, SRAM again invited cycling journalists to the Top of the World during Crankworx, this time to test the slightly down-market XO 11-speed group. That repetition might sound odd, but only until you realize that these two groups are nearly identical.

Like its predecessor, XO1 is designed for a single front chainring and features a massive rear cassette with 11 cogs that range in size from 10 to 42 teeth. The chainrings (they are available in several sizes) feature SRAM’s X-Sync tooth profile, which alternates between fat and narrow teeth and helps prevent the chain from falling off the ring. The straight-parallelogram derailleurs are also very similar. In fact, the 1,525-gram X01 group weighs just 52 grams more than the XX1, suggesting that there’s little physical difference between the two.

The groups are also similarly priced, which has already sparked debate. The new XO1 group costs $1,497—about $160 less than the XX1 group. That’s not insubstantial, but it’s not even 10 percent less. That raises a question: If XO1 weighs and costs nearly the same as XX1, what’s the difference?

We spent the recent ride down Top of the World (it’s a long trail, there was lots of time) trying to find out. Of primary concern: Does XO1 shift as well as its slightly more expensive sibling? It didn’t take long to realize that not only does the new group work just as well as its predecessor, it actually felt more polished than the XX1 group. Shifting felt quick and crisp—it’s not smooth like Shimano’s, but the chain moves with precision and intent. When set up properly, which takes a little more time than with a 2x10 system, the derailleur moved through the gears quickly, and it consistently kept the chain on our selected cog. While the cassette has the same gear range as the XX1 version, there are some slight differences. Notably, the XO1 cassette weighs 30 grams more, mostly because it has less machining (it also has a black coating compared to the XX1’s silver finish).

The X01 cassette features a massive cassette, with cogs that range in size from 10 to 42 teeth. (Matt Phillips)

As on the XX1 group, the X-Sync tooth design on the front chainring worked superbly. Whether I was bouncing over rocks, or whipping through high-speed chatter, my chain stayed on. The shift paddle of this group has a different shape than others from, but I didn’t notice a change in performance or comfort. When I asked about the shifter, SRAM said new sculpted profile might make its way to other groups in the future.

Because our test ride involved one, long descent (4,926 vertical feet, to be exact) and little climbing, one of the more substantial differences between the groups went unnoticed. The new X01 crank uses a standard 94mm bolt circle diameter (BCD), a measurement that represents the spacing of the chainring bolt holes. That’s larger than the XX1’s 76mm BCD. What’s the difference? XX1’s smaller BCD accommodates chainrings with as few as 28 teeth; the smallest ring X01 accepts has 30 teeth. That’s not a huge jump, but some riders who routinely suffer up long and steep pitches might take issue with those two extra teeth. On the plus side, SRAM is also making X-Sync rings with a standard 104 BCD, which will allow riders to convert their existing drivetrain to a 1x system that benefits from the wide-then-narrow tooth profile.

During our test, the carbon crank arms felt stiff, yet not remarkably so. That came as little surprise, however; they’re the same arms used on SRAM’s popular XO series. The arms have a smooth, thin profile that easily accommodates shoes with thicker soles, like those made by 5.10.

Even after just a single day riding X01 in Whistler, it became apparent that this new group is so good that in most cases, it gives riders few reasons to choose XX1. The facts are just too substantial to ignore: It weighs about the same, costs less, and performs better. For all we know, SRAM might have plans to significantly improve XX1 down the road (by reducing weight or possibly even creating an electronic group), but for now the choice between X01 and XX1 isn’t really a choice at all.